This invention relates to a sonar towed array and, more particularly, to a ribbon strength member splicing method and apparatus for a high-strength, thin-line towed sonar array.
Generally, sonar arrays are towed up to a mile or so behind the towing vessel. The towed array is deployed by unwinding it from the spool of a winch, on which it is stowed when not in use. The array may be on the order of 1500 feet in length and one inch in diameter, and is generally made in sections or modules of about 90 feet in length, which are joined together by means of an electro-mechanical coupling. An internal strength member runs the length of each module, and functions to carry the tensile load on each module, mainly caused by drag of the array is it is towed.
The strength member in each module carries the principal accumulated stress of the array. Each strength member must be connected to a termination member to transfer the tensile load of the strength member to the electro-mechanical coupling at each end of a module. The tensile load, of each module is thus successively transferred to the next forward module, until the entire load of the array is passed through the forward-most strength member termination and electromechanical coupling to a steel tow cable and thence to a towing vessel.
Some modules are acoustic modules, and contain sensitive acoustic sensors. In order to provide space for the sensors and to prevent unwanted acoustic signals from being passed to these sensors, a flat or ribbon-type strength member is employed in the acoustic modules. This ribbon-type strength member is arranged inside the walls of the tubular jacket of the module so that it does not have mechanical contact with the sensors, to minimize the transfer of unwanted acoustic signals.
Kevlar, a synthetic material produced by E. I. DuPont de Nemours & Co., is frequently used as the strength member in military and commercial towed sonar and sounding arrays. See U.S. Pat. No. 4,160,229 to McGough, and U.S. Pat. No. 4,090,168 to Miller, et al. Kevlar is an aramid, which is the generic name for a distinctive class of aromatic polyamide fibers. Kevlar has an extremely high tensile strength, and greater resistance to elongation than steel.
Kevlar is very difficult to secure at the end terminations because, although it is very strong in tension, it is very easily damaged when it is secured in conventional ways. It has been found that one of the best ways to terminate a strength member made of Kevlar ribbon braid is to splice the ends together to form a continuous loop, and to pass the loop over smooth, large radius pins on the termination members.
In splicing the ends of the Kevlar ribbon to form a continuous loop, it was found difficult to make reproducible, identical splices of consistent high quality, strength and performance. There was a tendency for each splice to be different, with many mistakes being made during splicing, without the mistakes being recognized by the splicer.